As an apparatus for recording and reproducing signals on/from a tape magnetic recording medium, a rotary drum type of video cassette recorder apparatus is widely used wherein a track is formed at an inclined angle for record on the tape magnetic recording medium by the magnetic head which is mounted on the rotating drum, and reproducing is also performed by tracing this inclined track. Above all, in recent years, a rotary drum type of VTR apparatus of the digital standards has come into wide use.
As an example of the tape magnetic recording medium, a coat-type of magnetic tape is available. Its structure is such that a magnetic layer or a magnetic surface is formed on a plastic substrate coated with needle-like or fine grain magnetic particles by a binder which is an adhesive agent. As to the magnetic surface, as the recording is performed in high density, its coercive force Hc and its residual magnetic flux density Br tend to increase. In the case of the MP tape of the DV standards, for example, the coercive force Hc reaches 2300 oersted and the residual magnetic flux density Br reaches 3000 gauss.
On the other hand, the size of a magnetic particle simple substance is micronized to a degree of 0.1×1.0 μm in the case of a coat-type metal tape. Moreover, a tape thickness becomes thinner from the tape thickness of approximately 10 to 16 μm adopted in the conventional editing machine because of the demand for a compact tape cassette and a long time recording and reproducing. In the case of the tape magnetic recording medium for digital video signals of the DV standard, the tape has a thickness of 7 to 8 μm.
Accordingly, the apparatus for recording and reproducing on/from the magnetic tape having such characteristics needs to be elaborately designed on both hydrodynamic interference function in relation to the control of physical contact with the magnetic tape and magnetic interference function in relation to the recording and reproducing.
As an example of such a magnetic tape recording/reproducing apparatus, the conventional rotary drum type head for recording and reproducing on/from the magnetic tape medium while rotating adopts a magnetic head according to the magnetic induction principle. This magnetic head has both the magnetic poles opposed to each other by keeping a narrow head gap in-between and the magnetic surface of the magnetic tape medium is disposed orthogonal to this head gap in the closest position. At the time of recording, when the lines of magnetic force generated by driving both the magnetic poles reach from one magnetic pole to the other magnetic pole through the head gap and the magnetic surface, the magnetic substance constituting the magnetic surface is magnetized so that the recording is performed, while at the time of reproducing, a leakage magnetic flux generated from the magnetic substance constituting the magnetic surface of the magnetic tape medium is caught by both the magnetic poles through the head gap and an electromotive force generated by electromagnetic induction when the medium fluctuates while moving is detected so that the reproducing is performed.
In order to enhance the recording density and to improve a S/N ratio, adherence of the magnetic tape medium to the head gap is required and, furthermore, maintaining a steady movement of the tape while keeping the adherence is required.
In the conventional configuration, in order to realize the above described adherence state, a contact pressure is obtained by pressing the magnetic tape medium against the head gap and, above all, the rotary drum type head is constituted in such a manner that the above described contact pressure, so-called “contact” is obtained by a tensile force given to the magnetic tape medium. FIG. 10 is a schematic view explaining the configuration of such a conventional rotary drum type head. FIG. 11 is a diagram viewed from the direction of arrow A in FIG. 10 and FIG. 12 is a diagram viewed from the direction of arrow B in FIG. 10.
As shown in each drawing, a rotary drum type head 100 disposes a magnetic head 104 having a head gap 103 in a head window 102 caved in so as to open a part of the cylindrical surface of a cylindrical rotary drum 101 and rotates at a predetermined velocity in the rotational direction 106. With this rotation, the magnetic head 104 also moves at the same velocity. On the magnetic tape medium 105 along the rotary drum 101, a tensile force 107 is given, and pulled by this tensile force 107, the magnetic tape medium is pressed against the head gap 103 and advances at the velocity slower than that of the magnetic head 104 in the same direction. Moreover, at the bottom of this rotary drum 101, there is disposed a cylindrical fixed drum 111 at a short distance apart.
Here, in order to improve a contact state between the head gap 103 and the magnetic tape medium 105, a surface 108 which contacts the magnetic tape medium 105 existing in the vicinity of the head gap 103 is constituted as a curved surface of a convex curvature 109 in the recording track direction, that is, in the magnetic tape running direction and moreover constituted as a curved surface of a convex curvature 110 in the track width direction also and moreover the surface 108 is constituted as projecting from the cylindrical surface of the rotary drum 101 together with the head gap 103.
When the magnetic tape medium 105 contacts the magnetic head 104 thus constituted by pressure attributable to the tensile force 107, the magnetic tape medium 105 is deformed in the convex shape along the surface 108 of the magnetic head 104 so as to improve the contact state. Moreover, the part in which the magnetic head 104 does not contact the magnetic tape medium 105 is sometimes deformed by influences of the clearance between the head window 102, the rotary drum 101 and the fixed drum 111.
As described above, the rotary drum type head 100 as conventionally constituted gives the sufficient tensile force 107 to the magnetic tape medium 105 and by this tensile force 107 the magnetic tape medium 105 is compulsively pressed against the convex magnetic head 104 so as to improve the contact state, and by practicing magnetic interference between the magnetic head 104 and the magnetic tape medium 105 the magnetic recording or reproducing is performed.
However, as a result of pressing the magnetic tape medium 105 compulsively against the convex magnetic head 104 as described above, the problems arise that the head gap 103 is worn and the head gap life is shortened. Other problems also arise that the magnetic surface of the magnetic tape medium 105 is also worn and the tape life is shortened due to non-reversal deformation.
Hence, in order to lengthen the life of the head, in the conventional configuration, a depth of the head gap 103, that is, a gap was designed to be deep enough to dispose a margin there. According to this configuration, for example, at the initial stage, the gap is set to 20 to 30 μm so that the time until the gap depth reduces to the limit value due to wear is lengthened and the life of the head is extended.
However, the configuration where the initial gap depth is deeply set presents the problems in that the improvement of sensitivity has a limit, a high density recording is controlled and a high density reproducing has a limit. Moreover, it did not have any effect on solving the problem of the shortened life of the tape.
Moreover, it also does not realize a means with which an MR head and a GMR head of the magnetic resistance effect type (or magnetic flux response type) having a configuration where the magnetic field changes on the recording medium are detected with an extremely shallow gap by utilizing the magnetic resistance effect, which are mainly applied in a hard magnetic disc drive (HDD), can be applied in the tape magnetic recording medium in place of the magnetic head based on the above described magnetic induction principle.